Poka yoke is a lean manufacturing tool that refers to “mistake-proofing” or “error-proofing” a process. In Japanese, poka yoke translates to “avoid” (“yokeru”) “mistakes” (“poka”).
When a mistake reaches the customer, it becomes a defect. Poka yoke aims to prevent defects by catching, correcting, and eliminating mistakes at the source.
History of Poka Yoke
The term “poka yoke” was coined by Shigeo Shingo, a key contributor to the the Toyota Production System (TPS), in the 1960s. Shingo noticed that in one process at the Toyota plant the workers often forgot to place a required spring under a switch button. He redesigned the process to be completed in two steps: first placing the required springs in a placeholder, then inserting the springs into the switch. As a result, if a spring remained in the placeholder, it would be clear to the worker that they had forgotten to place it in the switch. Then, they could correct their mistake immediately.
Shingo originally called the technique “baka-yoke,” or “idiot-proofing,” but changed it to the milder “poka yoke,” or “error-proofing,” after an operator became offended.
Poka Yoke Examples
The principles of poka yoke have been applied across industries. For example, preventing mistakes before they occur is critical in the medical industry; failing to prevent even a tiny mistake can have tragic consequences. Having measures in place to mark the correct body part for surgery, and even enforcing the washing of one’s hands, can prevent serious consequences.
Poka yoke is also present in our everyday lives. For example, microwaves are designed to stop running if the door is open to prevent waves from escaping, and many new cars have error-proofing features such as alerts that let the driver know if the car is leaving a lane. Some examples of poka yoke are so commonplace that we often wouldn’t think of them. For example, we often take for granted the spell-checking functions on our phones, internet browsers, and software that prevent us from making spelling mistakes in our communications.